How to send mail in UNIX Shell Script?

#!/bin/bash
RETVAL=`<<EOF
SET PAGESIZE 0 FEEDBACK OFF VERIFY OFF HEADING OFF ECHO OFF
SELECT 'shivam' FROM dual;
EXIT;
EOF`
if [ -z "$RETVAL" ]; then
  echo "No rows returned from database" | mailx  -s "TEXT...... is corrupted" shivam.kumar91@gmail.com
  exit 0
else
  echo $RETVAL
fi